While technology has often been given “black box” status, where it is expected to be able to contribute to enhanced motivation, more active engagement in learning activities, and enhanced autonomy (Stockwell & Reinders, 2019), language teachers ought to reflect on their beliefs in the use of technological tools, the role of technology in ELT, and the technology-based practices in real classroom contexts. This study investigated Taiwanese EFL teachers’ perceptions of the usability of the two well-known vocabulary learning platforms, Quizlet and Memrise, in terms of their technical and pedagogical usage in ELT classrooms. The factors that influence EFL teachers’ perceptions and practice of technological tools in ELT classrooms were also explored. The rudimentary survey and the follow-up semi-structured interview were administered in this study. The results show that most of the EFL teachers embrace the potential and the strength of the two computer-assisted vocabulary learning (CAVL) tools, having enjoyable experiences and some of them also propose some practical techniques to integrate CAVL tools in ELT classrooms. The pedagogical implications are discussed in this study.